Fertilizers are responsible for over half of global food production, but there are areas in world with nutrient deficiency and other areas of nutrient excess.
Managing mineral plant nutrients requires careful application of science and skill to meet production, environmental, and social goals.

Wednesday, September 19, 2012

The 4R's... Is it all about the Application Rate?

Fertilizer spreader

It
seems that discussions by government regulators to minimize nutrient
impacts immediately turn to reducing the rate of fertilizer application.
While this approach has the advantage
of simplicity and being easy to measure, a narrow focus on fertilizer
application rate alone will consistently fall short of achieving the
desired environmental and economic goals.

Selecting the Right Rate of fertilizer
application is only one of the 4R’s that must be considered when making
nutrient decisions. In addition to
selecting the Right Rate, it is also essential to choose the Right
Source, the Right Time, and the Right Place to get the maximum value.
When one of these 4R’s is changed, it is necessary to evaluate how it
impacts the remaining 4R factors.

Here are a few examples of how only modifying the fertilizer application rate may not achieve the desired results:

• It is important that growing crops have the
right combination of all nutrients present in the rootzone, especially
during periods of peak demand. If the nutrient supply during these
critical times is not adequate to support growth then crop yields and
quality will suffer.

• Nutrient applications should be made as close to
the time of plant uptake as feasible. Some nutrients can be placed in
the soil in advance of plant uptake because of their limited mobility;
however other nutrients are at risk of loss if they remain in the soil
for an extended period of time.

• When organic materials are used as a plant
nutrient source, a period of mineralization is required before the
nutrients are converted to a form that can be taken up by roots.
Sufficient time is required for mineralization to synchronize nutrient
release with plant uptake.

Elephant manure spreader?

• Adequate soil moisture is needed for dissolved
nutrients to be taken up by roots. Uncertainties in rainfall patterns
make the prediction of fertilizer rate an ever-changing target each
year. When crops are irrigated, nutrient loss is closely associated with
water distribution and irrigation uniformity across the field.

• There are numerous examples to show that when
plants are not supplied with a balanced and appropriate supply of all
the essential nutrients, none of them will be fully used to their
potential. For example if a soil is low in K, then nitrate will not be
properly taken up and may be more prone to leaching loss.

• Some fertilizer sources are more suitable for
placement close to the seed than other sources, which may cause damage
to germinating seedlings. Placing fertilizer close to the seed can
provide some early-season growth stimulation in some circumstances.

Examples of controlled-release fertilizer

• Technology can be used to help keep nutrients in
the proper place. For example the use of a nitrification inhibitor may
reduce both nitrate leaching and denitrification losses from some N
fertilizers. Similarly, a urease inhibitor can minimize ammonia loss and
improve nutrient recovery from urea applied to the soil surface.

• Controlled-release technology can reduce the
risk of nutrient loss and eliminate the need for multiple trips through
the field to apply fertilizer. Enhanced nutrient recovery by plants is
often reported when these nutrient sources are used.

• Custom blends of fluid fertilizers allow a
precise combination of nutrients to be delivered to the soil in each
drop. Each droplet provides uniform and consistent nutrition to the
plant. Some compound fertilizers and additives are formulated to control
the soil environment around the granule to enhance plant nutrient
recovery.

Fertilizer is essential to sustaining food production

These few examples illustrate how an overly narrow
focus on fertilizer application rate alone can cause growers to miss
their overall objective—that is growing a high yielding and high quality
crop that is both economically profitable and environmentally sound.
When the 4R Nutrient Stewardship approach is implemented on each field,
it is clear that no one of them can dominate nor be excluded. It is NOT
all about the fertilizer application rate, because the source, time, and
place decisions must all be considered to get the rate right.

No comments:

Post a Comment

Followers

About Me

I am a soil scientist with interest in managing plant nutrients in the best way possible. I am fortunate to be able to work in research and education to be able to accomplish this goal.
After receiving a PhD in Soil Science at the University of California (Riverside), I worked as a Research Scientist for the U.S. government, as a Professor of Soil Science, and now I work for a not-for-profit institution. It's been a wonderful experience!